Known three-way catalytic converters with good activity and endurance use one or more catalytic components from the platinum group metals, such as platinum, palladium, or rhodium which have been deposited on a refractory oxide carrier, for example aluminum oxide with a high surface. They are conventionally applied in the form of a thin layer or coating to a suitable carrier or a suitable substrate such as a refractory ceramic or metal honeycomb structure. In this connection the demand for improved catalyst activity and service life has led to complex catalytic converter designs which comprise several catalyst layers on support structures, each of the layers containing selected carrier materials and catalytic components and so-called promoters, stabilizers and oxygen storage compounds.
Document DE 501 06 490 T2 discloses an economical, single-layer, high performance three-way catalytic converter which contains a catalytic coating with platinum, rhodium and various oxide materials on an inert carrier. In this connection platinum promotes the oxidation of hydrocarbons and carbon monoxide, while rhodium promotes the reduction of nitrogen oxides.
Against this background, the object of the invention is to design an improved device for exhaust emission control in an internal combustion engine which ensures, in case of a fault, that the oxygen storage unit of the catalytically active coating for exhaust emission control can still adequately absorb or release oxygen.